Towering 10 stories above the banks of San Francisquito Creek, the El Palo Alto redwood predates the U.S. Constitution by more than 800 years. It is widely believed to have been a campsite for explorer Gaspar de Portola when he discovered San Francisco Bay in 1769.

It has endured everything from ecological changes to economic shifts, all of which left marks on the ecology of this venerable tree. Now it’s entangled in the debate over high-speed rail.

The tree stands within 10 feet of existing Caltrain tracks between the Menlo Park and Palo Alto stations, with commuter trains passing by 90 times every weekday. Initial plans by the California High-Speed Rail Authority called for widening the tracks to accommodate the new rail line, which would put the tree in jeopardy. Proposed alternatives included a trench or raised track.

To be sure, critics cite many reasons for their opposition, including the costs. But in Palo Alto and neighboring communities, the tree has become a budding symbol for why high-speed rail — approved by a majority of the state’s voters in 2008 — needs to be evaluated carefully. Dave Dockter, Palo Alto city arborist and current steward of the tree, said, “I think all of the alternatives have a potentially significant and catastrophic potential to impact the El Palo Alto redwood.”

For example, he said, relocating the train tracks could disrupt the tree’s root system.

“The environmental review information [submitted by the city of Palo Alto] has already stated that the placement of any alternatives must be addressed to protect the root plate to prevent catastrophic toppling of the entire tree,” Dockter said. “I think that is one of the first issues that need to be resolved and discussed before the High-Speed Rail Authority can even make it to first base in creating minimal impact to this tree.”

High-Speed Rail Authority officials emphasized that protecting important historical and environmental treasures is a priority. Spokeswoman Rachel Wall said the authority is completing a series of environmental reviews, each addressing increasingly localized concerns.

“There was the broad, program-level [Environmental Impact Report] for the Bay Area, for the Central Valley and for the state,” she said. “Those are really the big, overarching, program-level environmental certifications that we did back in ’05 and then in ’07 and in ’08. What we’re doing now is project level work where it’s more specific and it’s broken down by the 10 segments in the project.”

The initial Environmental Impact Report briefly mentioned the El Palo Alto redwood as a key historic resource but did not get into details about ways to protect it. The report did address how the high-speed rail project would affect El Palo Alto visually, calling the impact minimal because the tree dominates the landscape.

In a recent interview, Wall said, “I know that the Caltrain right-of-way is very close to that tree. I’ve heard you can reach out and touch it, essentially. But certainly our project will avoid, minimize or mitigate that impact wherever possible … in all likelihood, avoiding it, because it’s such a historical resource for our state.”

El Palo Alto is a coast redwood, a species best known for producing some of the tallest and oldest trees on Earth. Some redwoods have grown as tall as 30- or 40-story buildings and have lived for more than 3,000 years. Redwoods have long been a symbol of the conservation and environmental movement, influencing, most notably, Sierra Club founder John Muir.

Ruskin Hartley, executive director of the Save the Redwoods League, said, “If I look at the whole sweep of conservation efforts, I would argue, to a large degree, they started with the redwoods. In 1864, one of the first conservation acts, protection acts, was the Federal Government setting aside the Mariposa Grove of giant sequoias and the Yosemite Valley for protection. Redwoods themselves have inspired protection acts going back at least 150 years.”

Coast redwoods are rare trees, found sporadically along the Northern California and southern Oregon coast. They are considered a vulnerable species by the International Union for Conservation of Nature. “In the last 150 years, more than 95 percent of the ancient coast redwood forests have been logged,” Hartley said. “Today, anywhere that we find ancient monarch trees that are a relic of the past is a place we need to work to protect.”

Among redwoods, El Palo Alto itself is an anomaly. Very few coast redwoods are found naturally this far into the valley and even fewer are as old or tall as El Palo Alto. El Palo Alto is estimated to have stood on the banks of San Francisquito Creek for 1070 years.

Yet, Dockter pointed out, “It is only been in the last century that mankind has had an effect on the tree, which are manifold. Many, many effects have influenced the tree both above-ground and below-ground. Incidentally, there are other conditions that are even beyond the railroad’s effect on the tree, and one is just our human culture has actually altered the water table in the Santa Clara Valley, which I believe had a dramatic effect on the health of El Palo Alto.”

Early photographs show that El Palo Alto once had two trunks. The widely held belief is that one trunk was washed away in a storm in the 1880s. Dockter is not so convinced. “There’s another controversial thought that maybe the tree came out of necessity for the previous wooden trestle to be put in. There is no record of the actual event that took that second spar out, whether it was a storm or whether it was actually Southern Pacific Railroad crews that could have taken it out on a weekend or something and it just didn’t get reported in the local media,” he said.

The tree is an important symbol for the Peninsula region. It is featured on the seals of Stanford University and the City of Palo Alto. An anthropomorphized version of El Palo Alto has served as the unofficial mascot for Stanford athletic teams since the early 1980s and has even been featured in a commercial for ESPN’s Sports Center.

Trains have impacted the tree’s health for the past century and a half. Until the advent of diesel in the middle of the 20th-century, trains powered by the combustion of wood and coal would storm past the tree, leaving layers of soot that would effectively suffocate it in layers of carbon. Dockter noted, “The first carbon footprint impact was to the El Palo Alto redwood from smoke, actually.”

El Palo Alto is a symbol of survival. As Hartley put it, “I think what this story shows is just how resilient these trees can be if we don’t cut them down. That tree has had just about everything thrown at it with the exception of a saw; its top has died back, and its lost limbs and its lost a trunk, but the tree is still there.”